Sam , I am not sure that you will notice any great difference with the low end of the 9.0 Koncept with the 9.8 Formula . The Koncept being noticably lighter and a bit softer will be far easier to pump . Where the Formula has the advantage is at the top end where it,s extra battens and cams really lock in the draft and make the sail super stable even when overpowered .
Where are you ? perhaps we can arrange a demo sail ?